Electron discharge device



July 26, 1949. P, L, SPEN ER 2,477,317

ELECTRON DISCHARGE DEVICE Filed March 21, 1945 2 Sheets-Sheef l July 26,1949. A P. SPENCER ELECTRON DISCHARGE DEVICE Filed March 21, 1945 I I I1 11 a iiiRiis Patented July 26, 1949 UNITED STATES PATENT OFFICESELECTRON DISCHARGE DEVIGE Percy L. Spencer, West Newton, Mass asslgnorto Raytheon Manufacturing Company,.Newton,

Mass a corporation of Delaware Application March 21, 1945, Serial No.583,922

tune the tube so as to vary the frequency ofthe oscillations generated;by the tube. It is also desirable thatpthe tuningarrangement havesubstantially in inertia so that the frequency generated by the tube maybe modulated at a very high rate. In this way the tube may befrequency-modulated in accordance with a desire signal variation. 7 1

One of the objects of this invention is to DI'Q- vide a novel andeflicient means for varying the frequency oscillations generated by thetube.

Another object of this invention is to devise such a means which issubstantially inertialess.

The foregoing and other objects of the invention will be best understoodfrom the following description of exemplifications thereof, referencebeing had to the accompanying drawings where vention, said sectionbeingtaken along line l--.-l of Fig. 2; 1 1

' Fig. 2 is a transverse cross section taken alonglineZ-J of Fig. 1;

Fig. 3 is a fragmentary'view partly broken away wise formed ofconducting material. The hollow cylindrical block I has formedupon itsinterior surface a central annular projectionl to which is soldered aplurality of suitably spacedradially disposed plates or arms 5. The arms5, block l and end caps 2 and 3 constitute the anode structure. Theinterior ends of the arms 5 form anode faces for receiving electronsemitted from a cathode Gcentrally disposed within the anodestructure.

'Ihe cathode 6 is preferably of the indirectly heated oxide-coated,thermionic, type provided with anouter electrically conducting sleeve!within which is contained a heater coilinot 9 Claims. (01. ze -27.5,

Fig. 1 is a transverse section through a magnetron constructed inaccordance with my in-;

shown), the .end conductors 9 and ill of which project from-oppositeends of the cathode 6. one. of the said conductors, the conductor ill.for: example, may be connected to. said outer ,con-

ductive sleeve! whereas the other conductor 9. is

insulated from said sleeve. Light conductive shields ll and 12 arepreferably mounted at, the

outer ends Of. the cathode, sleeve 1 so. as to Dre-r vent electronbeams. from being projected out-r wardly toward the end caps! and 3 fThe cathode 6 is supported by apair of lead-in, conductors l3 and. I lconnected respectively to the conductors 9 and Ill. The lead-inconductors l3 and ll. are sealed through glass seals l5 and. I B mountedrespectively in the outer ends of conducting pipes 7 l1, and I8 which,in turn, are hermetically sealedthrough the wall of block I.

When a, tube as described above is placed be-. tween suitable, ma neticpoles l9 and,.2ll,,,the cathode heater is. energized, and a suitablevolt-- age is, impressed between the cathode and the. anode structure,oscillations will be generated, Each pair of alternate anode arms5-together. with the portion of the block I therebetween con-L stitute acavity resonator. Each cavity resonator.

contains a certain amount of capacitance be tween the arms 5 and also acertain amount of inductance. This capacity and inductance primarily dte mi the res nant eq e y of h cavity resonator and thus the frequencyofwthe oscillatio s generated. These oscillations may be led out of saiddevice by a coupling loop 2| ex:- tending into one of the cavityresonators. One,

end of the coupling loop is connected to the inner,

end of the conducting pipe 22 which is hermeti cally sealed through thewall, of the block L. The other end of said coupling loop is connectedto a, conductor 23 which extendsjthrough said pipe 22 and emergesthrough a glass seal 24 car ried Jay the outer end of said pipe 22. Theconductor 23 together with an external cylinder pipe (not shown)connected to the pipe 22form a po axial conductor transmission linethrough which the oscillations may be led to a suitable utilization:

device.

In order to reinforce, the main frequency at which the device isintendedto oscillate and to suppress spurious oscillations, eachalternate; anode arm 5 is connected at one end thereof by' a conductingstrap 25'.

intervening alternate anode arms are connected by a similar strap 26'.This insures that thevolt' By the term strap" I intend to include anelongated conductor of any" cross-sectional shape, here shown asrectangular. At the same end of the anode structure, the

ages at the alternate anode arms are maintained in phase with eachother. In order to avoid spurious oscillations due to voltagedifferences arising because of the length of the anode arms along theaxis of the tube, those anode arms which are interconnected by the strapare similarly interconnected by a strap ZI at the lower ends of saidarms, while those anode arms which are interconnected by the strap 26are similarly interconnected by a strap 28. It will be noted that acapacity exists between the straps 25 and 26 and likewise betweenthe-lstraps fl and 28. These capacities constitute apart of the capacityof each of thefresonant cav' iesas.'

described above. g Also sealed through the wall of the block Isubstantially equal to .one wave length will re- ,flect a relativelylow-resistive impedance into the adjacent one end thereof is.aiconducting pipe 23 withinewliich is mounted a central conductor. v 38so as to form a concentric transmission line therewith; The inner end ofthe conductor may be connected. to a conductor '3! -'of reduceddiametenwhich, in turn, is connelct'ed'to one of the straps, forexample, the strap'2 5f It will be noted that the s'trap 25' will haveimpressed thereon "the voltage conditions at the end of one; set ofalternate anodefarins. fThef-"pipe 29.,v on the other hand, will haveimpressed upon it the voltage conditions of the anode blockj'l whichwill be substantially the voltage conditions existing at the back'ofeach cavity resonator. In this way, the oscillatin'g' voltage which isgeneratedv by the ube will be impressed on the'concentric transmissionline 29-30. 'At theouter end of the conductor 30, there is mounted ahollow conductingcsleeve '32'preferably of nickel;

This sleeve is externally coated with therirnioi iic emiss'lvegoxides 33whereby the sleeve 32 is enabled to function asathermionic cathode.Within thejsleeve' 32 is supported aheatingfilament 3,5 the outer ends35 of which extend through a 7 an inductive impedance into the cavityresona- 7 tors of the magnetron. so

glass stem 36 sealed in the outer end of the pipe 29 .Thus, when theconductors 35 are connected to a suitable source of energy such .as abattery 31, the filament 34 raises the temperature, of, the sleeve 32to, apoint at which the coating 33 emits electrons.

When oscillations are generated by the mag-Q netron, the oscillatoryvoltage will bepropagated through the concentric transmission line 23 7-31].v When this voltage is of the =proper phas e .to' make the pipe 29.positive with respect to the conductor 30 at thesleeve 32 electrons willnow fromthe sleeve 32 through the intervening space to the. pipe 29.This electronicv flow will tend.

to cause this portion, ofthe concentric transmission line to act as alow impedance termination and therefore the concentric transmission line..29 30 will act as a stub ,line terminated by a'low impedance end. I

.In order to introduce tuning variations I surround the sleeve 32 with agrid 38.. This. grid preferably consists of a winding of finewiresupported on a conducting standard 39-.- The outer end of this standardis likewise sealed through; the stem 36 so as to providean externalelectrical connection to the grid, The .grid 38. In Fig. Zthe grid 38 isshown as having a variable pitchwinding, the pitch ;of the windingincreasing asthe distancefrom the blockzl increases; Thus is oftheso-called variable mu type.

as the grid 38 is made more negative with respect tothe sleeve 32,electronic flow will first be out 01f at the end closest to block I. ofthe grid becomes more negative, emission; W ll If the voltage jlifconeentric transmission line terminated by a low impedance end andhaving a length v cavity resonators of the magnetron. Thus, if

the voltage on the grid 38 is set so that cut-off of the electronic flowoccurs at the center of the coating 33, the concentric transmission line29-30- will appear substantially as such a re-' sistive impedance. Ifhowever the voltage on the-grid 38- is made less negative, cut-off willoccur closer to the block I and the effective length ofthestubline willbe shortened. This will pro-- duce the result that the stub line willreflect On the other hand, if the voltage on the grid 38 is mademorenegative, cut-off will occur further awayfrom the block I and the stubline will reflect a capacitative reactance into the cavity resonators.Thus merelyby varying the potential on the grid 38, varying amounts ofeither inductive or capacitative impedance maybe reflected into thecavity resonators. This will change the natural frequency at which thesecavityresonatorstend to oscil-' late and thus the desired tuning of themagnetron will occur.

Any desired arrangement for introducing the necessary voltage variationson the grid 38 may be-utilized. This is shown diagrammatically in. Fig.2 as-a batteryv Bl having a potentiometer 4.0

connected across it. The positive end of the battery isconnected to thepipe 29' while an adjustable tap 4| is'connected through a,currentlimiting resistance 62 to the grid standard '39;

By adjusting the tap 4|, the voltage on the grid .38 may be varied so astoproduce tuning. Of

course it is to be understood that the voltage vari ation on the gridmay be produced by any desired means such, as, for example, a signalvariation of any desired frequency. For example, frequencystabilization: may: be secured by making the voltage variation on thegrid 38 responsive;

to the deviations of the frequency of theoscillations generated by themagnetron from a desired frequency. The grid 38 may take any one ofa.variety of forms as long as it shifts the cut-ofl value along the gridin response to voltage variations therein. For example, an alternativeformof. grid .is shown in Fig. 4. In this arrangement, the gridturns aresubstantially uniform in pitch but gradually increase in diameter fromone end to the other. Various other equivalent constructions whereby agrid having variable cut-off along its length maybe devised. 3

Instead of utilizing a single themnioniccathodealong which theelectronic discharge cut-off may be varied, an alternative arrangementsuch as shown in Fig. 3 may be utilized; In this arrangement the samereference numerals are used where parts are identical with those shownin h mb9. m nt.o .12is 1. and Fiesta aerial:

43 and similarly carries a. short-coated section 46 of emissive oxides.The sleeves 42 and 45 may be heated by heating filaments 41 and 48,respectively, connected in series and mounted within said sleeves 42 and45. The outer ends 49 and 500i the. heating filaments 41 and are sealedthrough the stem 35. A substantially unitormly wound grid surrounds thecathode sleeve 42 and a, similar grid 52 surrounds the cathode 45. Thesegrids are mounted respectively on grid standards 53 and 54 which arelikewise sealed through the stem 36.

1 In thislatter arrangement, if grid 5| is biased so as. to. permitelectronic flow between the emitting section 43 and the pipe 29, theconcentric line will be terminated substantially at the emitting section43. If however, the grid 5| is biased to cut off the electronic flow andthe grid 53 is biased. so as to permit electronic flow from the emittingsection 46, the concentric line will be terminated substantially at saidemitting section 45. A variation in the length of the termination ofsuch a stub line through substantially a quarter .wave length willproduce substantially a maximum of variation in the reactive impedancere flected by the stub line into the cavity resonators of the magnetron.Thus ifthe distance b between the emitting sections 43 and 46 is madesubstantiallyequal to a quarter wave length, substantially maximumtuning may be effected by shifting the emission from one cathode to theother. .Instead of having an abrupt shift of the terminus of theconcentric line from one cathode to the other, such transfer ispreferably made gradually and in this way tuningmay be accomplished,over the entire range afforded by the two. limits of theefiectivetermination of the concentric line. This is illustrated diagrammaticallyin Fig. 3 by the provision of two batteries B3 and 64, respectivelyhaving their positive terminals connected together and having tworesistances 55 and 56 connected respectively across batteries 63 and 64,respectively. An adjustable tap 51 on the resistance 55 is connected tothe grid standard 53 while an adjustable tap 58 on the resistance 56 isconnected to the grid standard 54. The two taps 51 and 58 may be movedsimultaneously by a common actuating member 59. This arrangementprovides a potentiometer in which one grid is made progressively morenegative while the other grid is made progressively less negative. Inthe extreme position of actuation of member 59, one of the grids willpermit a full conduction while the other grid will cut off conduction.The other limit of ad- .lustment of the member 59 will reverse theconditions at the grids. Intermediate positions of adjustment willrepresent intermediate conditions of tuning. Here, likewise, it is to beunderstood that the variations in voltage on the grids 5| and 52 may beaccomplished automatically in response to any desired variation.

Of course it is to be understood that this invention is not limited tothe particular details as described above inasmuch as many equivalentswill suggest themselves to those skilled in the art.

-What' is claimed is:

1.: An electrqmdischarge device comprising; a. cavity resonator, -means,adjacent thereto for exe citing said resonator to produceoscillationstherein, a. concentric transmission line coupled to saidcavity resonator, said line comprising a hollow outer conductorenclosing a central cone ductor, an electron emissive section on saidcentral conductor at a predetermined position removed from thepoint atwhich said line'is coupled to said resonator and means adjacent saidemissive section for cutting ofi the electron flowfrom: said emissivesection to said outer conductor at'variable points along the'length ofsaid emissive section whereby the effective impedance of said line i asreflected into said cavity resonator is: varied;

2. An electron-discharge device comprising a cavity resonator, meansadjacent thereto for exciting said resonator to produceoscillationstherein, a concentric transmission line coupled to saidcavity resonator, said line comprising a hollow outer conductorenclosing a central. conductor, an electron emissive section on. saidcentral conductor at a predetermined position removed from. the pointatwhich said line is coupled. to said resonator and a control electrodeadjacent said emissive section.

3. An electron-discharge device comprising a cavity resonator, meansadjacent thereto for ex.- citing said .resonator to produce oscillationstherein, a concentric transmission'line coupled to said cavityresonator, said line comprising a hollow outer conductor enclosing acentral conductor, an-electron emissive section of substantial lengthonsaid centralconductor at a predetermined position removed ,from thepoint at which said line is coupled to said resonator and a controlelectrode adjacent said emissive section, said control electrode havinga cut-off character istic which 'variesfrom one end of said emissivesection to'the other end thereof, whereby the effective length of 'saidemissive section capable of passing electrons to said outer conductormay be varied to vary the efiective impedance of said line as reflectedinto said cavity resonator.

4. An electron-discharge device comprising a cavity resonator, meansadjacent thereto for exciting said resonator to produce oscillationstherein, a concentric transmission line coupled to said cavityresonator, said line comprising a hollow outer conductor enclosing acentral conductor, an electron emissive section of substantial length onsaid central conductor at a predetermined position removed from thepoint at which said line is coupled to said resonator, the length ofsaid emissive section being approximately a quarter of the wave lengthof the average oscillations generated in said cavity resonator and acontrol electrode adjacent said emissive section, said control electrodehaving a cut-off characteristic which varies from one end of saidemissive section to the other end thereof, whereby the effective lengthof said emissive section capable of passing electrons to said outerconductor may be varied to vary the effective impedance of said line asreflected into said cavity resonator.

5. An electron-discharge device comprising a cavity resonator, meansadjacent thereto for exciting said resonator to produce oscillationstherein, a concentric transmission line coupled to said cavityresonator, said line comprising a hollow outer conductor enclosing acentral conductor, a pair of electron emissive sections on said centralconductor spaced from each other conductor whereby the efiectiveimpedance of said'line as reflected into is varied.

6. An electron-discharge device comprising a cavity resonator, meansadjacent thereto for exciting said resonator to produce oscillationstherein, a concentric transmission line coupled to'said cavityresonator, said line comprising a said cavity resonator hollow outerconductor enclosing a central con- I ductor, a pair of electron emissivesections on said central conductor spaced from each other and from thepoint at which said line is coupled to said cavity resonator and meansadjacent said emissive sections for regulating the electron flow fromeach of said emissive sections to said outer conductor in oppositedirections whereby the effective impedance of said line as reflectedinto said cavity resonatoris varied.

7. An electron discharge device comprising a cavity resonator, meansadjacent thereto for exciting said resonator to produce oscillationstherein, a concentric transmission line coupled to said cavityresonator, said line comprising a hollow outer conductor enclosing acentral conductor, apair of electron emissive sections onsaid centralconductor spaced from each other and from the point at which said lineis coupled to said cavity resonator and a control electrode adjacenteach of said emissive sections for regulating the electron flow fromeach of said emissive sections to said outer conductor whereby theefiective impedance of said line as reflected into said cavity resonatoris varied.

8. A magnetron comprising a hollow conducting member, a cathodecentrally located therein, a plurality of spaced radial arms extendinginwardly from said hollow member and terminating adjacent said cathode,alternate anode'arms being connected together by. a conducting strapadjacent one end of said arms, a concentric transmission line comprisinga hollow outer conductor enclosing a central conductor, said central conductor being connected to said strap, said outer conductor beingconnected to said hollow conducting member, an electron emissive sectionon said central conductorat a predetermined position removed from thepoint at which said central conductor is connected to said strap andmeans adjacent said emissive section for regulating the electron flowfrom said emissive section, to said outer conductor.

9. .A magnetron comprising a hollow conducting member, a cathodecentrally located therein, a plurality of spaced radial anode armsextend-' ing inwardly from said hollow conducting member and terminatingadjacent said cathode, alter.- nate anode arms being connected togetherby a conducting strap adjacent one end of said arms, a concentrictransmission line comprising a hollow outer conductor enclosing acentral conductor, said central conductor. being connected to saidstrap, said outer conductor being connected to said hollow conductingmember, a pair of elec-' tron emissive sections on said centralconductor spaced from each other and from the point at which saidcentral conductor is coupled to said strap and means adjacent saidemissive sections for regulating the electron flow from each of saidemissive sections to said outer conductor.

PERCY L. SPENCER. I

REFERENCES CITED The following referen ces are of record in the file ofthis patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,477,317July 26, 1949 PERCY L. SPENCER It is hereby certified that errors appearin the printed specification of the above numbered patent requiringcorrection as follows:

Oolu nn 1gl life 11, for the Words in inertia read no inertia; column 5,line 7, for thus rea t is;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case 1n thePatent Office.

Signed and sealed this 13th day of December, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommz'ssioner of Patents.

